FIELD OF THE INVENTION
The present invention relates to a water heater having a plurality
of heating elements as described in the preamble of claim 1.
Such a heater is known, for example, from US Pat. No. 5,020,127.
BACKGROUND OF THE INVENTION
(also referred to as "tankless" or "instant" heaters)
work with one or more chambers, which are generally only slightly larger
as the heating elements and the water when flowing instantaneously
can heat to a set temperature. Flow heaters are
for a long time as conventional
Superior to water heaters with large storage tanks
known. The problems with conventional
Water heaters are u. a. their inability, a sufficiently fast
Regulation for the
Provide high performance power supply as required
is to set the target temperatures over the
wide range of states
to provide that in normal household and commercial applications
usually occur. In particular, this is the inability
problematic, a high-temperature overshoot without shutdown
at flow stop
as a result of latent heat
and the rapid buildup of limescale deposits in the water heater
in areas with hard water.
To secure the commercial success, must pass or tankless
Heaters a variety of powerful heating elements as well
have a scheme based on flow and pressure changes
responds very quickly to maintain a constant regulated temperature.
For better understanding
The difficulties to which both are subject are the
Addressed obstacles to which instantaneous water heaters are exposed.
For example. has shown that flow rates of
at least 2.25 gpm [1 gpm = 3.785 liters / min] at 120 ° F [° C = (° F-32) * 5/9]
are required to lead the way of life in most industrialized nations
to meet typical household application. Depending on the location, the water source
and the season the water temperatures are in the range of 38 ° F to over 90 ° F,
the single-source instantaneous water heater is a typical
minimum heating input of at least 28 kW or about 95,000
BTU [1 BTU = 1.055 kJ]. For electrical resistance heating elements
The power density must not be neglected. heating elements
High power density show a much shorter service life than such
low power density. To reach 28 kW and the benefits
to get a small heating system is a water heater
preferred with several heating elements.
Part of the prior art before 1975 taught the use of heating elements
firm food service. Because in household applications fluids with weak
(less than 1 gpm) to moderate (to
3 gpm) flow
were to be heated, units of fixed feed were certain
Subject to restrictions.
With moderate flow was enough
this out to the heat
to receive and maintain a target temperature. In weak
However, a high fixed feed rate will dangerously overheat the water
and cause the danger of scalding the user. The
in the run with fixed power supply thus limited the performance and required
Devices for flow activation,
the switching on of the heating elements prevented until a safe
was reached. It is a temperature of the inlet water of 60 ° F or more
accepted; then heating elements are fixed feed power of total
28 kW at a current
from less than about 2.25 gpm very dangerous. For that reason were
electric water heaters with fixed feed power in general
limited to 9 kW (about 30,000 BTU) and worked best
as individual devices
at the job site.
in the development and design of a commercially acceptable water heater
Home operation to be considered
Points are described below.
Instantaneous water heaters with multiple heating elements are designed with small heat exchangers whose power / volume flow ratio is relatively high. As described in the prior art, the water flowing through satisfactorily absorbs the heat in heating operation and discharges it; however, when switched off, the latent heat in the heating elements raises the water temperature to very high levels. This circumstance is exacerbated in prior art step-wise or follow-up control circuits. In these designs, the heating elements, which generally sit in their own separate heating chambers, one after the other energized, with a first, energized full power heating element depending on demand downstream, another full-energized heating element is switched on, etc., until successively all needed to reach the target temperature Heating elements are constantly excited. When switching off (shutdown), the elements are de-energized. In some schemes, the powerless switching of the heating elements takes place in succession, wherein first the last switched on and then successively the remaining heating elements are switched off until all are de-energized. In all systems, at least one element or more has been working at full power; it contains a significant amount of heat, which then passes to the very small amount of stagnant water in the heat exchanger or the respective chamber. The result would be a strong overheating of the heating elements, most of which are still energized in the event of flow disruption, and thus overheating of the adjacent fluid. This excess temperature can result in scalding hot water - especially in on-site single flow water heaters where the distance from the heater to the dispensing point is very short.
the element, the hotter
the water and the more lime falls
out. This is especially problematic in hard water areas. consequently
Another disadvantage of cyclic overheating of water is
Turn off the resulting accelerated formation and accumulation
of lime deposits
on the overheated
Heating elements and in the heat exchanger.
As a result of the relatively small
Chambers used in instantaneous water heaters build these deposits
itself up very quickly, so that the service life of the heating elements and / or
of the heat exchanger
for the formation of lime deposits
in the water heater can
mineral substances with water over connecting wires
in the filter screens of household appliances and appliances - dishwashers and washing machines,
Taps - are flushed
to an undesirable
The main objectives of the water heater is, water as needed quickly
to heat. The most common in instantaneous water heaters for temperature sensing
used elements are thermistors. The respectively used
Thermistorart is subject to cost restrictions and their response time
when detecting a temperature change
can be in the range of two seconds. Coupling this reaction time
with the duration before heating
the thermistor for heating a resistance heating element and then
the water is needed,
As it turns out, the overall delay is about seven
Seconds lie. Consequently, the rules in
known water heaters to pendulum controls with considerable
Hysteresis of the working temperature. At 70 ° F inlet temperature is the volume flow rate
of water at 120 ° F
normal shower room about 1.5 gpm. A 28 kW heater can handle 1.5 gpm of running water
at about 2 ° per
Heat up the second.
of seven seconds and the - above
described potential overheating problems
are made of instantaneous water heaters with several high-performance heaters
Everyone knows the effect of opening
an additional one
Fitting to the water temperature of a shower jet. You use
a hot water source with a relatively constant temperature,
such as a storage thermal, it is quite easy, the ratio hot / cold water so
set to reach a set temperature again. at
a water heater with a high hysteresis control
is this different. The reaction is running
the temperature effects of rapid flow changes afterwards, so that
the temperature in annoying
Because pressure changes
also the flow
influence, the same annoying temperature fluctuations apply
for pressure changes.
Pressure changes usually,
when the water supply comes from a private network. Even in community
or city networks, the pressure can vary greatly depending on demand.
a water heater several sampling points or fittings over normal
Distribution lines, temperature changes are buffered by the latter.
If the heating heats up too much, part of the heat is taken from the pipes and
with the flowing through
Mixed water to mitigate the effect of small temperature fluctuations. The same
applies if the heating control system fades too far as a result of the hysteresis.
Water heater water over
delivered to the target point
the pipes take on some of the heat
and they could
over at a temperature
the set point. Below the set point, the cooler water mixes
partly with the warmer;
the heat surplus
in the pipes is also partly given back to the water.
This buffering effect can be useful in household applications,
where the pipes from the heater to the fitting are light
ten meters long or longer
continue in power grids high voltage spikes and compensation or
it is for
a regulation important to the triacs and other electronic and
Protecting semiconductor devices that are switched with. At the
this is done with overvoltage protection elements,
working with metal oxide varistors. However, these elements are power limited
and are destroyed by too strong peaks and overshoots.
US Pat. Nos. 5,216,743, 5,020,127, 4,604,515, 4,567,350, 4,511,790, 4,333,002, 3,952,182, and 3,787,729 recognize the utility of multiple heating elements in a water heater and the benefits of sequencing the same. to improve the operational temperature control. US Pat. Nos. 5,216,743 and 5,020,127 also teach controls with a stepped modulation of the heating elements, which are switched at zero crossings, for the hysteresis of the temperature control as well as to reduce interference in lighting circuits. The U.S. Patent 4,337,388
and the EP 0 209 867 A2
recognize the need for better temperature control to avoid overheating, and apply a bias circuit and modulation control. The U.S. Patent 3,952,182
and said European patent teaches an initial venting of the heating chamber before or at the start of operation. The U.S. Patent No. 5,216,743
teaches that gases are generated during heating and works with continuous ventilation to prevent damage to the heating elements or the heating chambers and to mitigate the possibility of dangerous overheating during operation if the temperature sensor is no longer flushed by the fluid.
Most commercially available thermistors take about two seconds to respond to a full temperature change. This interval can be referred to as the time constant of the thermistor. In a water heater, where the thermistor is secondarily heated due to the thermal delay, a systematic response delay occurs. This thermal delay is inherent because the heating element must be heated prior to the fluid to which the thermistor is responsive. In a water heater of the type disclosed herein, the system time constant required by the thermistor to respond to the full temperature change is about seven seconds. In the known heaters, the heating elements are activated one at a time, with a first heating element being activated first and continuously. The temperature change from activating the first heating element is compared with reference point voltages and used to generate a demand signal. The amount of demand so derived is a function of the system temperature time constant. With increasing demand relative to temperature changes and system time constant, indicating the need for additional heating, successive heaters are sequentially activated from zero to full 100% excitation. Heating elements can be added until enough work is done to reach the setpoint; compare the U.S. Patent No. 5,020,127
, In most applications, less than the total number of elements are activated to reach the set point so that the on / off switching factor of the initially activated heating element is significantly longer than that of the last activated one. The activated heating elements are therefore disproportionately hotter than in the areas where the heating elements are not activated. If the heating elements are de-energized in reverse order until shutdown, localized overheating points may occur as one or more elements are energized at full power in the absence of flow. Over time, the effects of this heat distribution imbalance can damage the heat exchanger and significantly shorten the useful life of the overloaded heating elements. In hard water areas, these localized overtemperatures occurring at shutdown also cause excessive formation of limescale.
The present invention overcomes the disadvantages of the prior art.
It reveals an improved water heater that has a controller
better regulation of the power supply to each of a variety of heating elements
starts. The techniques of the invention
are particularly suitable for
use in a multi-chamber water heater with
each one of the heating elements.
SUMMARY OF THE INVENTION
The present invention provides a water heater having a plurality
Heating elements ready, coming from one or more power supplies
be fed. The water heater has improved control
with a temperature sensing and a Vorhalteschaltung.
The control is with temperature sensing elements
coupled whose output signals modified circuit technology
to increase the time constants from the thermal delay
Compensate, which is normally used in temperature sensing
continuously heated, different degrees of flowing fluid occur, so that
one obtains time-corrected values of the instantaneous temperature. The
Control also has an improved supply and temperature sensing circuit
on which the excitation of the heating elements due to time / flow constants
controls. The electric power supply of the heating elements is provided by the
Controlled logic of the control circuit.
The current is first applied to the controller by energizing relays; Thereafter, the heating elements are incrementally energized or de-energized, with triacs switched by trigger elements at zero crossing. The scheme includes logic as well as a solid state controller, by means of which the incremental increase or decrease of the excitation of the heating element takes place in stages down to half a period of the feeding current. The switching on or off of the current to and from the heating elements is controlled so that each heating element from the current source receives the same power as distributed by the controller in successive steps of the half periods of the sine wave. A first heating element is first activated or deactivated at the zero crossing of an electrical half period. The successive and remaining heating elements are then alternately activated and deactivated in the subsequent half-period zero crossings, so that the power supplied to the heating elements is divided among them in approximately equal proportions becomes; Thus, the on / off switching ratio of the elements in operation is constantly balanced and the increased or decreased instantaneous simultaneous activation of all heating elements regulated to very small Leistungszu- or -abnahmeschritte. As a result of this even distribution of power, the electrical loading of the heating elements is almost perfectly balanced (in both single-phase and three-phase systems); This also eliminates the disturbances that normally cause the switching of high power heating elements in lighting circuits, as well as the pre-loading of transformers. Furthermore, this power distribution minimizes localized heating in the heating system. With properly dimensioned heaters, they require less than 50% power in most water heating applications, with all heaters operating at substantially the same level of activity. At shutdown, the latent heat in any one of the heaters is usually one-half or less than in the known sequential heaters where normally one or more of the elements operate at full power. The temperature overshoots as well as the formation of limescale due to the latent heat in the elements are significantly reduced, so that the useful life increases.
An object of the present invention is to provide a water heater
To specify a controller, according to a principle of power sharing
the energy supply to the heating elements alternately increasing and decreasing
incrementally regulates the temperature sensing and control behavior in the
Sense of a more accurate operational temperature control.
According to a related object of the present invention is a water heater
be provided with a scheme that controls the heating elements
uniformly excited in a continuous power dividing process.
It is also an object of the present invention to provide a controller for water heaters
specify with the several heating elements alternately excitable
are that fed
Power is divided equally among the elements, so that
at the flow-free
Move down the latent heat
evenly distributed in all elements
becomes. In which one the latent heat
reduced in the heating elements, also decreases their shutdown temperature
and it will grow evenly
the adjoining fluid is distributed so that the failing and
on the elements or in the heat exchanger
Reduced amount of limescale reduced. A peculiarity of the present
Invention is the provision of a water-flow heater,
in which the formation of limescale remains minimal.
It is a peculiarity of the present invention, the incremental
Increase and decrease in the power supply to high-performance heating elements
after a power sharing process and incrementally down to
to control electrical half periods; this can be the simultaneous
reduce the momentary electrical load on the heating elements and
with it disturbances
virtually eliminate in lighting circuits and transformers.
After a related feature of the present invention is
a water water heater provided with a scheme
the power to all heating elements according to a power component principle
each so allocates that the arousal each in very small energy impulses
and evenly distributed on the elements
will increase or decrease alternately.
Yet another peculiarity of the invention is a water heater, the
Improvements to the temperature sensing and Vorhalteschaltung provides,
around the thermal delay
to overcome in the detection and response time, for a uniform and
quickly reaching the setpoint and for a quick shutdown
at flow stop
The water heater preferably has a control with improved
and Vorhalteschaltung and / or logic on, with a uniform and
quickly reaching the setpoint at minimum hystere and a
fast shutdown when flow is interrupted
without the use of mechanical means for detecting the
Another peculiarity of the present invention is a water heater
with a control according to the power part principle, in which the heating elements
be fed from several sources. The heating elements of a water heater
can each be fed from one of several power sources.
Another special feature of the invention lies in a controller for a
Water heater for
a uniform load
several power supply connections - in particular
at three-phase - ensures.
Leaves a water heater
to regulate himself so that he the mains connection evenly and
Another special feature of the invention is an overvoltage protection for a
Water heater, the triacs or other circuit breaker in front
Destructive voltage peaks from the supply connection protects. The
Separation in the waiting mode can be achieved with relays for the selection of
Facilities that are normally open, so in this waiting state
no voltage is applied to the triacs.
is an advantage of the present invention that the water heater
has a scheme that controls the system control and regulation
with a microcontroller.
a significant advantage of the present invention is that by the
improved regulation increased acceptance of instantaneous water heaters
by the users.
to the invention are still the relatively long service life and
the low maintenance costs of a water flow heater according to the invention.
and other objects, features and advantages of the present invention
will be apparent from the following detailed description based on the
Figures in the attached
BRIEF DESCRIPTION OF THE DRAWINGS
1 generally shows a multi-chamber instantaneous water heater according to the invention;
2 shows a temperature amplifier, a circuit arrangement and a graph of the output voltage versus the temperature according to the present invention;
3 shows a suitable set point circuit according to the invention;
4 shows an exemplary turn-off circuit according to the invention;
5 shows an exemplary inventive wait circuit;
6 shows a pulse width modulator which can be used according to the invention;
7 shows a modulation detector;
8th shows a typical switching order for different points in time according to the present invention;
9 shows an exemplary, optically coupled heating driver for the heating elements;
10 shows an optically coupled heater driver for a selected heating element;
11 shows a magnetically coupled heater driver;
12 shows a driving circuit for relay drivers;
13 shows a suitable shift register control;
14 shows a network synchronization amplifier;
15 shows a circuit according to the invention, which operates with a microcontroller;
16 shows a current control circuit, which in the arrangement according to 15 can be used;
17 shows a suitable compensation circuit for correcting the delay of the current temperature information;
18 shows a suitable Vorhalteschaltung for estimating the speed of the change in temperature; and
19 shows in block diagram an alternative microprocessor according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED
The 1 shows the general structure of an embodiment of a multi-chamber water heater according to the invention 10 , The instantaneous water heater has two substantially identical dual chamber modules 26 . 36 connected to a flange connection 14 connected to each other. A suitable instantaneous water heater may operate with a single chamber module, but preferably combines two or more dual chamber modules in series with a suitable flange connection between them, as discussed below.
During operation, water flows through the supply line 13 to; the attached heat sink keeps the solid state power switches for the heaters described below at a safe working temperature. The water inlet temperature is controlled by a thermistor 18 controlled, either at the bottom of the water supply line 13 or disposed in a chamber upstream of the first heating element. The water flows down into the first chamber 20 in and up on and over the heating element 22 , At the top of the chamber 20 The water flow is controlled by a high temperature limiter switch 24 monitored for overtemperature. The water continues to flow through a clutch 25 with reduced flow area (throttle), which is the chamber 20 of the module 26 with its chamber 28 combines. The water is due to the increase in speed at the transition from the throttle coupling 25 in the chamber 28 mixed. At the top of the chamber 28 monitors the thermistor 30 the water temperature. The water level comes with a detector 32 up in the chamber 28 controlled. The water now flows through the chamber 28 down on and over the heating element 34 ,
Gas at the top of the chamber 20
flows horizontally from the outlet of the throttle coupling 25
in the chamber 28
through the ventilation opening 37
in the flange 33
that the modules 26
connects to each other, and then further horizontally into the chamber 38
of the module 36
, The gas takes a very small amount of water. For more details about the heat sink 16
, the throttle couplings and the ventilation between the modules is on the U.S. Patent No. 5,216,743
At the bottom of the chamber 28 of the module 26 is the water temperature of a thermistor 42 measured. The water is flowing through the throttle coupling 41 between the chambers 28 . 38 mixed. After the feed down in the chamber 38 the water flows upwards and over the heating element 44 and is from the limit switch 46 monitored for overtemperature. Gas continues to flow horizontally from the top of the chamber 38 through the throttle coupling 47 between the upper ends of the chambers 38 . 40 and is flowing through the throttle coupling between the chambers 38 . 40 mixed. At the top of the chamber 40 become the water temperature and the water level of the thermistor 49 or from the water level detector 48 supervised. The water temperature is also at the bottom of the chamber 40 from the thermistor 54 measured. The water continues to flow down and over the heating element 50 while gas continues horizontally from the top of the chamber 40 through the ventilation outlet 37 in the clutch 51 in the drain line 52 passes. The gas is mixed with the drained heated liquid and with it from the water heater 10 output. In operation, the gas from each of the heating chambers is continuously released. A small amount of fluid can go with the gas through the vent 37 in the clutch 51 escape. The temperature can be measured by looking at the thermistor 54 at the bottom of the chamber 40 , as shown, or in the drain line 52 arranges. The water is through a throttle coupling 53 further mixed, through which it leaves the chamber 40 in the drain line 52 exit; then it flows upwards over the entire length of the drain line 52 to the drain connection 56 ,
As can be seen, the hot water system has five thermistors. The thermistors 42 . 54 are located at the bottom of the heating chambers, the thermistors 30 . 49 at the top of the chambers 28 respectively. 40 and the thermistor 18 at the lower end of the supply line 13 , These thermistors are the number and position of the main measuring means for controlling the heating. It will be understood by those skilled in the art that their number and arrangement represent a preferred embodiment; both the number and location of the thermistors or other temperature sensors as well as their control temperatures can be tailored to the requirements of each application.
The high temperature limit switch 24 . 46 are located in the top of the chamber 29 respectively. 38 , These are preset temperature switches with a normally closed contact that only opens (and breaks the electrical connection) when a preselected high temperature condition exists. If a switch opens, it remains open until it is manually or automatically reset, ie closed again. Here, too, it can be seen that the number and position of the high-temperature limit switches can be selected differently depending on the application.
The limit switches 24 . 46 are connected in series with the control signal for eight relays. The relays interrupt the wires of the power lines for all four heating elements on both sides, regardless of an approximately existing control command from the control electronics. This is a mechanical aid for detecting excess temperatures. In the event of overtemperature, the limit switch must be reset manually or automatically before the instantaneous water heater can start working again. The relays serve mainly as a safety device and overvoltage protection; their number and use are determined by the intended use of the heating system.
The water level detectors 32 . 48 record the water level in the modules 26 respectively. 36 , If the water level falls below the installation height of the detectors, all control relays are de-energized, which open the power supply to the four heating elements on both sides. If only the water level falls in the module 36 below its switching height, are preferably from the control relay, the heating elements 22 . 44 and 50 off. If only the water level falls in the module 26 below the switching height, is preferably the heating element 34 off. When switching off the heating element 34 leave the heating elements 22 . 44 and 50 Do not get excited about the rule logic, as described below. These water level sensors and circuits mainly have a safety function. Their use as well as the number and arrangement of the probes are preferably determined by the respective application.
The ventilation opening 37 in the clutch 33 at the top between the modules 26 . 36 as well as the ventilation opening 37 in the clutch 51 up between the module 36 and the drain line 51 (Acc. 1 ) allow the continuous discharge of air bubbles from the heating chambers in the water heater 10 , At the same time, however, the water can reach the target level in the chambers, so that the heating elements are not damaged.
To the housing of each of the heating chambers 20 . 28 . 38 and 40 is a settling tray 9 detachably attached. The settling bowls 9 can be essentially transparent to allow the operator to rule moderate intervals the maintenance requirement of the water heater can determine. The bowls 9 can be screwed to the associated housing, so that the removal and replacement easier for draining and cleaning the heating chambers.
The 2 shows a suitable temperature amplifier circuit 60 , Each of the five system thermistors 62 is preferably connected to its own amplifier circuit. The operational amplifier 63 sets the output of the thermistor to a linear positive output voltage 64 of about 30 mV per degree Fahrenheit within the operating temperature range of the water heater. The output voltage 64 is therefore proportional to the detected temperature. The 2 shows the linearity of the output voltage with the temperature. The circuit 60 contains a suitably scaled resistor 66 as well as a resistor 68 for setting the gain.
By means of the set point circuit 72 of the 3 the operator can set the output voltage of the water heater 10 to adjust. The temperature is adjusted by means of a manually adjustable potentiometer 74 , The set point circuit establishes two separate reference voltages 78 . 80 fixed, ie the high temperature cut-off voltage 78 and the working setpoint voltage 80 , In the preferred embodiment, the circuit also provides a minimum or default point to prevent freezing. The circuit 72 contains an operational amplifier 82 , The voltage 84 is to a - discussed above - inlet temperature booster 63 placed. The set point circuit 72 thus supplies the input voltages 80 . 78 to a shutdown circuit and the pulse width modulator as described below.
The high-temperature cut-off voltage 78 is an input signal of the comparator 86 the shutdown circuit 100 of the 4 , About the ratio setting resistors 88 respectively. 90 supply the temperature amplifiers 92 . 94 the second input signal 96 for the comparator 86 , The output voltage 98 The comparator has high state when the water temperature in the chambers 28 . 40 is below the high temperature cut-off voltage. If one or both chambers exceeds the high temperature cutoff voltage, the comparator output voltage drops 98 to zero, leaving the AND gate 104 of the 10 is locked. This will cause the heating element 34 turned off by its drive circuit, as in 10 shown and described below.
That of the circuit 102 in 10 controlled heating element 34 can be regarded as a sensing heating element, since its work is the control sequence for all other heating elements 22 . 44 and 50 initiates. Goes the output voltage of the Abschaltkomparators 86 of the 4 to zero, the heating element becomes 34 (the feeler heater) locked. By blocking the command voltage pulses from the pulse width modulator to the heating element 34 over the AND gate 104 (Comp. 10 ) all other heating elements are blocked (no signal to the sensing circuit 106 of the 10 ). Depending on the application, any of the heating elements may be used as the desired control or sensing heating element. The shutdown comparator 86 remains in the off state, as long as the output voltage from the temperature amplifiers of the chambers 28 . 40 ( 1 ) is higher than the high temperature cutoff voltage.
The standby circuit 106 of the 5 compares the (temperature indicative) voltage difference between the thermistor 30 up in the chamber 28 and the thermistor 42 down in the chamber 28 , The voltages from the thermistors go through a suitable resistor 112 respectively. 114 , The circuit 106 also shows the resistance 116 , the condenser 118 , the fast-charging element 120 , the resistance 122 and the amplifier 124 on. The output signal 126 the circuit 106 goes to a shift register 109 , as in 13 shown. The output voltage of the wait circuit assumes the high state when the thermistor 30 only a few degrees warmer than the thermistor 42 is how from the wait comparator 106 displayed. This H state locks a shift register 109 , by means of the shift register control circuit 108 gem. 13 the sequential activation of the heating elements 22 . 44 and 50 controls. The operation of the shift register will be described below. The H output of the comparator 110 of the 5 also turns on the heating elements 22 . 44 and 50 associated control relay 111 ( 12 ) de-energized.
Under normal conditions with water flow through the water heater 10 each chamber is hotter than the previous one. That's the chamber 40 hotter than the chamber 38 , this hotter than the chamber 28 and the latter hotter than the chamber 20 , When the flow stops, the latent heat in all the heating elements causes the water temperature in the chambers to rise. In this case, each chamber above is hotter than the bottom (thermocline) without flow. The comparator 100 the wait circuit, as in 4 shown, detects this condition and turns on the heating elements 22 . 44 and 50 from. The pulse width modulator (see below) holds the chamber 28 at a lower setpoint temperature and the chamber above hotter than below, so that the H output voltage of the hold circuit 106 (Comp. 5 ) and the water heater 10 remains in the waiting state.
Water flows through the water heater again 10 , is that of the thermistor 30 detected temperature close to that of the thermistor 42 captured. The output voltage of the comparator 110 the wait circuit goes to L level and switches the shift register 109 free, that the excitement of the heating elements 22 . 44 and 50 associated control relay 111 initiates. The control logic thus passes from the waiting to the operating or working state and the set point is returned from the waiting to the labor value. The heating elements are activated as required and search incrementally the working set point. Receives the water heater 10 over the working point preheated water, the regulation remains in the waiting state.
By comparing the temperature differences, as discussed above, in the present and / or absent thermoclinic state, so the comparator detected 106 the wait circuit the beginning and end of a flow through the water heater 10 , Approaching the chamber 28 above the temperature prevailing in a downstream chamber below, takes the output of the wait circuit 106 the low state and thus the water heater 10 from the waiting state. As in 4 shown is the shutdown circuit 100 at this time in the H state and the circuit indicates a flow state. If a flow is detected, the output voltage drops 149 the modulation circuit (see FIG. 7 ) to zero, all control relays are energized and become the shift register 109 (Comp. 13 ) unlocked.
The pulse width modulator 128 of the 6 receives six input voltages. The four amplifier output voltages 130 . 132 . 134 and 136 monitor the temperature in an associated chamber 20 . 28 . 38 respectively. 40 , The output voltage is from the associated thermistor 30 . 42 . 49 respectively. 54 derived. An input voltage is a control set point voltage 139 (manually or automatically specified). The input voltage 138 , which specifies the final set point, is the reference point for the temperature compensation of a supply thermistor 18 ,
The modulator circuit 128 contains an oscillator 140 which typically runs at 128 Hz. In particular, oscillates the oscillator 140 asynchronous to the mains frequency. The modulator 128 generates a positive square wave (typically 128 Hz) whose nominal duty cycle is in the range of 2% to 98%. The general function and operation of the circuit is apparent from the above description and the 6 ,
In the flow state, the positive input voltage of the operational amplifier A2 (OPAMP A2; 6 ) higher than the negative input voltage, so that the output voltage of the OPAMP A2 and the duty cycle of the output pulses slowly increase. Under these conditions, the triacs switch 164 ( 10 ) in the typical order for the current division operation. The increasing voltage at the output of OPAMP A2 is integrated with resistor R11 and capacitor C1 and buffered by voltage follower OPAMP A3. The time constant of R11, C1 is typically 30 s. This integrator damps sudden changes in the output of OPAMP A2. The positive output voltage of OPAMP A2 increases (within the limits of the heater) to continue until the Stromzu drove is reached, which provides the working setpoint temperature at the respective actual flow.
As the water warms up, the output voltage of the thermistor amplifier ( 60 in 2 ) too. As a result of the increasing output voltages of the thermistor amplifiers the input voltage difference on the OPAMP A2 decreases, the power supply to the heating elements is throttled. This control provides a smooth incremental power transition until all of the heating elements receive the correct heating power, while also maintaining the output temperature at the set point while sharing power to the heating elements. This smooth incremental transition occurs for any flow within the performance limits of the water heater.
It is now assumed that the water flow stops and the water temperature rises. As a result of the decrease in the input voltage differential across the OPAMP A2, the instantaneous water heater begins to incrementally reduce the power to the heating elements. Finally, the OPAMP A2 has reduced the duty cycle of the pulse width modulator so that no more power is applied to the heating elements. However, the latent heat of the heating elements causes the water temperature to rise above the predetermined cut-off point, so that the output voltage of the cut-off circuit 100 ( 4 ) assumes the L state and the heater driver for the chamber 28 is locked. It can be seen that when the heating element is switched off 34 all other heating elements are also switched off. The switch-off process also switches all control relays de-energized.
Almost immediately after switching off the chamber 28 above hotter than below. If this flow interruption occurs, the output signal decreases 149 of the modulation detector (cf. 7 ) the H state, all control relays are de-energized and the shift register is disabled. The regulation is therefore in the waiting mode. From now on, in the preferred embodiment, heat is applied by means of the heating relays 113 only to the chamber 28 laid as in 12 according to the wait circuit of 5 shown so that a minimum waiting target temperature is maintained to freeze to prevent. The power supply for maintaining the waiting target temperature and the temperature difference for the further waiting operation are very low.
If the temperatures in the chambers are far below the set point, the positive part of the generated square wave has a long duration. The width of this pulse, ie the duty cycle determines the proportion of power applied to the heating elements. If the positive part of the (driving) pulse has the H state for a larger part of the period, the output power (in watts) is high. If the positive part of the pulse has the H state for a shorter part of the period, the output power (in watts) is low). Is the drive pulse of the 10 in time with the zero crossing window of the optocoupler ( 9 ), the heating elements can 34 be controlled. The zero crossing window of the optocoupler is that portion of the line voltage near zero volts (typically 0 to 5 V) in which the opto-coupler can be enabled.
The pulse width modulator 128 Together with the thermistor amplifier, specifies the average proportion of power to be applied to each of the heating elements to maintain the discharge temperature at the setpoint. By calculating the average proportionate power and the rate of power change required for good temperature control, highly fluctuating current loads on the grid connection can be significantly reduced. A greatly varying power requirement causes the mains voltage to fluctuate considerably. The present arrangement - especially the alternative preferred embodiment to be discussed below - reduces or eliminates mains voltage fluctuations that could disturb lighting circuits, transformers and equipment connected to the mains.
The pulse width modulator 128 contains signal conditioning operational amplifier with an analogue output voltage, which typically varies between 0 V and +5 V. This voltage determines the duty cycle of the pulse width modulator. If the analog voltage is high, there is a need for a power supply to the heating elements. If the analog voltage drops below 0.7 V (no heating demand), a voltage detector outputs a positive output voltage, which switches off all control relays and thus the heating elements. This voltage detector is also referred to here as a modulation detector. When de-energized control relay all heating elements are disconnected from the mains or the power source, which is the normal state of the water heater 10 in the absence of water flow. The switching triacs are thus protected from voltage surges from the network, which could damage them. Such water heaters are daily little in operation; so it can be assumed that the triacs 85 a 24-hour day are protected.
The 7 shows a suitable modulation detector 142 for the current division operation of the heating elements. The voltage 146 is a positive reference voltage. Kick the tension 144 , which is proportional to the output voltage of the pulse width modulator, simultaneously with the zero crossing of the mains voltage, becomes a half period of the mains voltage to the heating element 34 placed. Turning on Triac # 2 will cause a logic pulse to go to a 4-stage shift register ( 13 ), which is clocked at 120 Hz in synchronism with the mains. The next clock pulse sets the first stage of the register exactly at the zero crossing of the mains voltage to the H level, so that the triac No. 1 turns on and a half-period of the mains voltage to the heating element 22 sets. The next clock pulse shifts the H output voltage of the register 1 to the entrance of the register 2 , This occurs at the zero crossing of the network; Triac # 3 will turn on and apply a half cycle of line voltage to the heater 44 , The next clock pulse shifts the H output voltage of the shift register output 2 to the entrance of the register 3 , This happens at the zero crossing of the mains voltage; Triac # 4 will turn on and apply a half cycle of line voltage to the heater 50 , An appropriate shift register control 108 is in 13 shown.
The pulse width modulator 128 initiated the switching of the heating element 34 for the duration of a half-period. The switching of the heating element 34 caused a logic pulse which was clocked into the register and the heating element 22 in the zero crossing for the next half period excited. The next clock pulse shifts the output voltage again, with triac # 3 passing through at zero crossing to the heater 44 for the duration of the next half-period. The next clock pulse pushes the logic pulse passing through the heating element 50 excited for the next half-period. The important feature of this method for switching the mains connection is that the heating elements are always switched on for the same amount of time, always in full periods. By always charging the grid for a full period, one eliminates the problems of half-period snubbing - including the problems in DC-biased transformers.
The switching of the heating element 34 causes a switching of the heating elements 22 . 44 and 50 in modulated half-cycle over two full electrical periods, as in 8th shown. It is assumed that all four elements have the same power; then the total current is out of Main power source to the heating elements equal to the only one heating element, which operates at full power, so as to obtain a current split in equal proportions. It can be seen that when the sensing circuit 102 in 10 detects the turn-on at each half-cycle of the network, the pulses are clocked by the shift register and all the heating elements supply the full and steady power. Turning on the triacs in sequence and in the zero crossings of the mains voltage also significantly reduces radio interference.
The optically coupled heater driver circuit 150 - Comp. 9 - for the heating elements 22 . 44 . 50 is identical. The output voltages of the individual shift registers go to a transistor inverter, which in turn drives the light emitting diode of an optocoupler. The command is given visually in a standard coupling to the input of the triac switch. The optocouplers belong to that design which switches the triac on at the zero crossing of the mains voltage. The heating driver for the heating element 34 corresponds to the drivers 150 with the exception that he switched through an additional sensing element gem. 10 which, as in 13 shown positive level on the shift register and initiates the current division process. As discussed above, with the driver circuit of the 10 any of the heating elements are controlled; it then performs the same control function as above for the heating element 34 is discussed. The optocouplers are available with reasonable breakdown voltages and can be used reliably in this application.
The 12 shows an alternative heating relay circuit 170 , which is magnetically coupled and provides protection against surges and unsafe working conditions. The heating relays 1 . 2 . 3 and 4 are the heating elements 22 . 24 . 44 respectively. 50 assigned as in 1 shown. The operation of the circuit 170 should be understood from the preceding description and the 12 be clear.
The circuit 152 is another embodiment and works as in 11 shown with an AND gate 154 at the entrance 156 a logic signal that occurs at the zero crossing of the network and at its input 158 a signal from the shift register lie. The output signal of the AND gate 154 controls a semiconductor switch 160 and this one pulse transformer 162 on the primary side, the secondary side via a current limiter resistor 166 the triac 164 controls.
the instantaneous water heater with full power, the power can be from the
Net be very high. The overcurrent switch
and the cable cross-sections should be sufficiently dimensioned
to absorb this current. In the present embodiment
a realistic installation provided several overcurrent shutters and supply lines.
It is assumed that the instantaneous water heater is in the waiting mode (compare the wait circuit 106 in 5 ). Since all control relays are de-energized, the chamber is 28 above hotter than below. The output signal of the modulation detector is in the zero state ( 7 ). A demand connection is made by allowing water at a temperature below the working set point to flow through the system. Is that from the thermistor 30 detected temperature similar to that of the thermistor 42 detected, the output of the wait circuit goes to the zero state, so that the water heater is switched out of the waiting state. At this time, the shutdown circuit is located 100 ( 4 ) in H-state, if the inlet temperature is below the predetermined shutdown temperature; the circuit thus reports the presence of a flow. (If the inlet temperature is above the set point, the water will not be heated.) When a flow is detected, the modulation detector output goes to zero and all control relays are energized and the shift register is enabled. Depending on the application, the water level detector can work with DC or AC. The water level detectors prevent overheating damage to the heat exchanger when attempting to operate the water heater without water in the chambers.
The 15 shows an embodiment with a circuit 180 using a microcontroller (MCU) 182 or another microprocessor system. Under control of the microprocessor, the output signals of the thermistors - as well as the setpoint signal - in a conditioning circuit 184 similar to the temperature amplifier the 2 read. The set point signal can be set with a potentiometer, a keyboard with field of view or a remote, analog or digital input device. From the processing circuit 184 the signal goes to an analogue to digital converter (ADC) 188 , a conventional circuit that may also be part of the microcontroller. The MCU may be any of many common microcontrollers or microprocessor system. The network synchronization circuit 168 (Comp. 14 ) may be a clock signal for the MCU derived from the network frequency for network synchronization. Network synchronization simplifies the power control algorithm. Alternatively, one can use a separate MCU clock and separate network frequency synchronization for the MCU. In the preferred embodiment, the shutdown circuit gem. 4 and the wait circuit acc. 5 included as software in the MCU. In this embodiment, there is no pulse Width modulator required. For the triac driver and the switching device, the circuit is gem. 9 or 11 suitable because a triac is a switch form. For product safety, the embodiment works gem. 15 also with water level detectors and high-temperature limit switches ( 1 ).
In the embodiment according to 15 are current transformers 189 to 15 or other current sensors together with voltage sensors to other inputs of the MCU. With these input signals, the control algorithm can improve the accuracy of the set point control. For this purpose, no further information is necessary because the skilled person from the disclosure of the preferred embodiment and the gem. 15 The software required for the MCU can easily be developed in order to obtain and evaluate status information about the heating elements using current transformers. This software can compensate for poorly located elements, power inequalities between them, leakage currents, and other abnormal states; Likewise, a rule support is possible due to the temperature rise per watt of feed power for a given chamber. One skilled in the art can thus develop the necessary circuitry and algorithms to achieve these goals or improvements with which the technology disclosed herein can be developed.
In order to keep the influence on the grid connection as low as possible, but the service life of the heating elements as long as possible, a regulation is essential, which allows full use of the grid periods and corrects mains voltage fluctuations that are faster than the eye inertia. A preferred method of grid connection control may be with a ROM memory as part of the control circuit 192 gem. 16 work. The circuit of 16 So can the pulse width modulator acc. 6 replace. In the preferred embodiment, the ROM is included in the microprocessor, although an external ROM may be used. In the ROM memory, the bit current of the half-period circuit of each heating element is stored. Each bit stream accounts for full-period usage and keeps the odd-numbered half cycles in certain bitstreams at a repetition rate faster than eye inertia (the flickering caused by fluctuating network loading is not noticeable). The ROM address is divided into two parts, the primary and the secondary address. The primary address locates in memory the start address of a bit stream for a particular level of performance. The secondary address is applied to a counter that clocks the stored bit stream to outputs where they are available for power control. In the preferred embodiment, 128 primary power control outputs may serve in increments of better than 1%; A 7-bit secondary address was used to clock a 128-bit bitstream.
Comparison to the small volume of water in the chambers of the heat exchanger
is the heating capacity
As a result of frequent changes
the flow rate is
a Vorhalteschaltung or a Vorhalterrgorithmus desirable
to the desired
To realize regulation properly. In the preferred embodiment
The provision is implemented by checking the speed of the temperature change
measures per unit of time.
given constant flow the
given correct power to the heating elements, the outlet temperature remains
constant at the set point. However, the flow suddenly increases
or from, the temperature detected by the thermistors sets a
Error is the thermal response delay of the thermistor and
the heat conduction of the
The circuit 194 gem. 17 is an improvement over the thermistor amplifier 60 gem. 2 and compensates for the delay of the actual temperature information. The time constant of R1 / C1 can be set to either get a time-corrected temperature, the correct instantaneous temperature, or an exaggerated temperature change for purposes of inventory. The output voltage of this circuit provides the lead information. In the embodiment according to. 15 the circuit is emulated by an algorithm using MCU control.
The 18 discloses a circuit 196 , which provides information about the temperature change per unit time. The output voltage of this circuit would include lead information. The circuit can also be according to an algorithm in the embodiment. 15 emulate.
The 19 shows an alternative circuit 190 that works with a microprocessor. The circuit acc. 19 So is an alternative for the circuit gem. 15 ,
The five thermistors TH 1N, TH 1, TH 2, TH 3 and TH 4 (corresponding to the thermistors 18 . 30 . 42 . 49 respectively. 54 of the 1 ) are arranged so that the heating chambers can be successively monitored for their temperature and their relation to a set temperature (higher or lower than these). This sequence of relationships then serves to derive the equation which best matches the power requirements of the heating elements to bring the temperature of the water flow at the outlet to the set point. These relationships also serve to monitor the flow of water.
the effect of a given, over a certain period of time
calculates the power levels applied to the heating elements
the speed of change
determine the water temperature. You compare this speed of change
with the difference between the water temperature at the system or
a chamber exit and a set point to determine how long
with a given level of performance still needs to be fed to
raise the water temperature to the set point. Is not the change
additional performance according to the stream splitting method described above
attach to each of the heating elements. Approaches the discharge temperature
the setpoint, one can reduce the power level to overshoot the
Set point to prevent. By prioritizing the performance level
lowers the setpoint, leaves
avoid that the heat stored in the heating elements that
Water over the
and then drops below him. These
Anticipating the power requirement to heat water to a set point
and without overheating
and the subsequent fall of the water temperature below the set point
is a special feature of the present invention. An embodiment
works with algorithms to time the temperature input signals
Heating elements are over
Triacs put on the net. The main causes of failure of these triacs
are voltage fluctuations and spikes from the AC network. Since that
System is mostly shut down, as described above, a method is desirable
to separate the triacs from the AC network. The Relaischaltung offers
the triac protection by opening the mains connection in the absence of heating demand. There
the system is typically shut off about 85% of the time
With this Relaistrennung the reliability of the triacs becomes considerable
power applied to the heaters is limited to only those that
to bring the water temperature to the set point, although this point of view
not the only one for
an effective operation. Did you want performance suddenly?
put all the heating elements at the same time, this need would affect the mains connection
act - eg.
with flickering lamps or a sinking of sensitive equipment such as air conditioners
and refrigerators available voltage
when connecting. To the annoying
To avoid flickering and the voltage drop, the inventive technique distributes the
Load on all heating elements, so not all the power requirement
and the system does not shut down suddenly as demand falls.
The present invention thus provides a performance-proportional as needed excitation with distribution to all heating elements. In one mode of operation, the voltage is applied in alternating half cycle pulses so that the heating elements each heat at about one quarter of the total power level. In case of falling demand and shutdown, the elements are de-energized in reverse order. The supplied power is at any time under all heating elements - in one embodiment, in equal parts - divided. The design requirements inherent in the water heater require models whose heating elements have sufficient power to provide hot water for the intended applications. Since most heating applications require less than 100% of the rated power maximum, the elements are operationally energized to less than 100% of their respective power. In contrast to the known methods of sequential activation in which a heating element is activated and kept activated while other heating elements are switched on, in the disclosed embodiments the heat in the water heater becomes 10 equally distributed. This avoids localized overheating during shutdown and overheating of the water in the event of sudden flow interruption and shutdown. This power sharing technique also ensures that heat is distributed evenly throughout the system during operation. The temperature micro-effects of changes in the power supply to the heating elements are more effectively, more uniformly and quickly controlled, so that you get a precise temperature control. The necessary algorithms can be accommodated in the software in the microprocessor.
A preferred embodiment of the present invention employs four 7 kW heating elements that are electronically connected in parallel and arranged in series with respect to the flow of water through the flow heater; comp. 1 ,
According to the invention, the heating demand from the system over a practicable period of time - for example, a second - continuously divided among all heating elements. The heating elements are preferably spaced in time and activated overlappingly, as in FIG 8th shown. The incremental load of the heating system increases with each half a period of the current, which is supplied to each connected heating element. Thus, all the heating elements are excited overlapping until the total power demand is divided as a function of the demand among the heating elements so that you reach the set temperature. Therefore, in most applications, the elements each operate over a practical time interval of one second with less than 100% power. While the power supply to the the same way, but is lowered in reverse, the heat is distributed more evenly over the total available elements, so that when switching off no localized overheating occur or they are at least significantly attenuated.
The heaters can be energized in alternating half-periods, as disclosed above, so that the time interval in the initial activation at a 60 Hz mains connection is half a period or 8.33 ms. As further explained below, the time interval between the activations of successive heating elements for reasonable temperature control may be up to 32 half periods (about 0.25 seconds), but is preferably eight half cycles or less. The significance of this time-spaced activation is that the demand is shared between all available heaters for a period of, for example, one second or more. This one-second interval is significantly shorter than the system time constant needed to display a full temperature change. The improved Vorhalteschaltung acc. 18 and the thermistor time correction circuit acc. 17 improve this type of regulation significantly.
Driving method according to the invention for
Activating the heating elements sets a very short and predetermined
Duration for power supply to the first activated heating element fixed. As
discussed above, the time span can be as short as a half period of
Be mains voltage. While
the half-period leaves
the power is divided into more than one heating element; a split
on several heating elements during
a half-period would
provide no significant benefit. Although above a time span
from a half period in detail
is discussed, this predetermined activation interval for the first
Heating element also be 2, 4 or 8 half periods. The predetermined one
Activation duration for
However, the first heating element is preferably shorter than 32 half periods, ie
for a 60 Hz connection, about a quarter of a second. As disclosed above,
the activation of the first heating element results in the same
Activation duration for each
other heating element in the system. With more than 32 half-periods of activation time
the first and the other heating elements would be the benefit of the invention
in terms of a precise
Control of the temperature of the water flowing through the heating system
According to the procedure. 6 the predetermined activation period of the first heating element was a half period; this gave the same predetermined activation period for all other heating elements. If the required heating load is very low, the half-period activation of each of the four heating elements may be followed by a relatively long shut-off interval of all the heating elements. As the load increases, the turn-off interval decreases until upon activation of the fourth heating element during its half-cycle, the re-activation of the first heating element during its half period immediately follows. At this point, the system operates at a quarter of its maximum power.
For any time interval greater than, for example, one second, it is important that the heating elements all be activated for the same length of time so that the load is evenly distributed. Before the heating element 1 is activated, a predetermined activation period is set; This duration then determines the activation duration of all other heating elements. In the preferred embodiment, the activation intervals of all the heating elements are equal to each other, so that the load is evenly distributed. Alternatively, one may activate the first heating element for a predetermined duration of, for example, four half periods, which then activates the heating elements 2 . 3 and 4 for a predetermined duration of, for example, two half periods would result. In any case, the activation period for each heating element is relatively short and, as explained above, preferably shorter than 32 half periods; the interval between the activation of the first and all subsequently activated heating elements is also relatively short and preferably shorter than 32 half periods. This short period of time is a function of the AC supply of the system, but is in any case only a fraction of a second.
It should be noted that, in some applications, it may be desirable for the controller according to the invention to first determine the last heating element in the flow path of the water - eg the heating element 50 gem. 1 - excited. Also, the controller can feed the fourth heating element continuously at full power during start-up so that it receives energy in each half-cycle. During startup, the third, second, and first heating elements initially activate, starting with successive half-period intervals, from the initial activation of the fourth heating element. The controller may regulate the power supply to the third, second, and first heating elements as described above, with the power supplied in half-cycle increments being distributed among the elements as needed. For example. you can fully activate the fourth heating element in each half-period from the start until 10 seconds later, the third, second and first heating element but every fourth half-period. Even at start-up, the half-period activation of the third heating element controls the half-period activation of the second and first heating elements. The advantage of this alternative technique is that at start-up the fourth heating element gets full power and therefore hot water is more readily available to the user. After the 10-s-run fintervall then the controller can switch to the operating mode described above, in which the heating elements contribute substantially evenly to the output from the flow heater output load. However, even in this embodiment, all of the heating elements contribute to the total output of the water heater during a relatively short period of time - one second or more.
an alternative embodiment
a serial data port is provided in the system over which
a duplex data transmission
possible with a remote place
is. With it
a mechanism with the setpoint temperature from the remote location
dependent on demand
raise or lower - eg.
for hotter water
for washing dishes
to shower. The skilled person can thus a working set point at about 110 ° F for the normal
Set demand, which can then only be raised if hotter water, for example.
is requested. This feature also reduces education
of lime deposits, since normally the heat demand
is lower, and also the line losses normally
occur when you get higher temperature
Temperature through the distribution system sends. This special feature
Power companies allow one at peak times
to warn you about lower energy consumption. Also you could use operational warnings
send to the remote location and thus the loss of a heating element
or report the interruption of the service if a limit switch
must become. The port also allows real-time, average
and send peak performance requests to the remote site.
It has already been discovered that the number and location of the thermistors can be changed depending on the requirements of the particular application. The arrangement of the thermistors can be compared to that in the 1 change shown. For example. can the thermistor 18 down in the chamber 20 and the thermistor 54 in the process 52 be arranged. In alternative embodiments of the invention, the high temperature cutoff voltage may be determined in any one or more chambers using the same or a similar location of the thermistors. It will also be appreciated that the wait circuitry may derive their noted voltage deviation signals from any two thermistors, with a first thermistor located at the top of a heating chamber and upstream of a second thermistor located downstream of the first thermistor.
the embodiments disclosed above
Triacs activated in response to a signal from optocouplers in zero crossings.
Instead of the optocoupler leaves
to use a proportional phase control to trigger the triacs,
However, as a result of their effects on radio interference as
The embodiments of a water heater described above relate to the use of a plurality of chambers, each with an associated heating element. It will be appreciated by those skilled in the art that the control of the present invention may also be used to control fluid temperature and to activate multiple heating elements in a single chamber or to control a single multi-section heating element in a single chamber, such as the one shown in FIGS U.S. Patent No. 5,020,127
describes. Thus, the individual sections of this heating element can be controlled in the same way as each of the heating elements disclosed here. Those skilled in the art will also appreciate that the present invention is particularly suitable for heating water for domestic and commercial use. However, the water heater may also be used to heat various other fluids, such as oil or other hydrocarbons, such as are used in various commercial or industrial applications.
Solar water heating systems typically have a storage tank for the heated water. After using this water, the recovery time required by the solar system to heat the water in the storage tank is relatively long. Also, if the solar heating is not available, the stored water must be heated. Meanwhile, the fluid storage function of a conventional water heater with storage tank is subject to all its inherent peculiarities - including energy lost during maintenance. Coupling a solar system with a heater disclosed here yields the benefit of an automatic, self-regulating and energy efficient system. The easiest way to close the process of the solar storage tank directly to the inlet of the heater 10 on and the expiration of the heater 10 normal to the hot water distribution pipe. Pours solar-heated water from the storage tank into the heater 10 , the temperatures are recorded in the manner disclosed here. As long as the preheated by solar energy water is warmer than the setpoint of the water heater, there is no power requirement; the heater 10 remains passive and does not generate heat. Falls the temperature of the solar storage tank in the water heater 10 flowing water below the set point, the latter leads him incrementally heat to maintain the set temperature steadily and constantly.
Heat recovery systems, the heat transferring me from a condenser coil, which is heated by the warm gases in the outlet of the compressor of an air conditioner or a heat pump, are becoming increasingly popular. In this system, the condenser coil of the air conditioning unit or heat pump is submerged in a water storage tank. Warming the snake by the warm gases transfers the heat to the surrounding water in the storage tank. As with the solar powered system described above, the ability to provide hot water may be provided by any conventional heating device in combination with the instantaneous water heater of the present invention 10 depend. The connections and complementary function of the instantaneous water heater according to the invention 10 when connected to a conventional fluid heating system, the same as described above for the solar application.
Gas instantaneous water heaters have been constructed for more than 75,000 BTUs. They are subject to minimum flow and minimum fluid pressure restrictions for reliable activation. For example, most high-performance safe activation models require a minimum flow of approximately 0.75 gpm. This limitation often results in false shutdown when the flow in applications such as bathing falls below the minimum activation flow. The water temperatures can quickly reach 80-90 ° F in summer; then the warm water volume tempered with cold water is so small that it often reaches the activation flow of these units. The initial activation and subsequent throttling of the hot water flow from a gas water heater may also cause the flow to fall below this minimum. An essential benefit can be achieved by using the instantaneous water heater 10 downstream of the gas flow heater. In this case, the water heater 10 be sized so that it provides enough heat only for flows below the activation flow of the gas flow heater. With increasing flow and activation of the gas flow heater, the heated water reduces the need for the flow heater 10 until the gas unit has reached its setpoint and then shuts off. The connection and the benefits of coupling a gas flow heater to the instantaneous water heater 10 are the same as described above for solar cell application.
above the invention for
It should be understood that the description is intended only for the purposes of
is used; the invention is not limited to these embodiments. For the expert
are alternative equipment
and operating techniques at hand.
FIGURE LABEL / LEGEND
- Voltage output Output voltage
- Temperature temperature
- 60-Hz oscillator
- reference voltage
- NOR gate
- TRIAC No. ... triac no ...
- Logic pulse logic pulse
- Drive pulse drive pulse
- Optical coupler optocoupler
- Relay relay
- Zero crossover logic zero crossing logic
- Drive pulse drive pulse
- High temp shutdown high temperature shutdown
- Optical coupler optocoupler
- Relay relay
- Sense feeling level
- Zero crossover logic zero crossing logic
- Drive pulse drive pulse
- Heater heating element
- Line sync zero crossover Network synchronous zero crossing
- Relay relay
- Heater ... relay relay for heating element ...
- network synchronization
- signal conditioning
- A / D converter
- Heating element heating element
- Multiplexer Multiplexer
- Relay relay
- Relay driver Relay driver
- Setpoint set point
- Signal conditioning Signal conditioning
- Thermistors Thermistors
- Triac driver Triac driver
- Water level detector ... water level detector and temperature limit switch
- Clock clock
- Counter counter
- Line sync network synchronization
- Primary address ... Primary address
(Page), represents performance level
- Secondary address Secondary address
- A / D conversion section Analog / digital conversion
- Communication control ... Data transfer control
- Conditioning circuit conditioning circuit
- Crystal time base Quartz time base
- EPROM section EPROM memory
- Heating element heating element
- Line sync network synchronization
- Local serial port Serial communication port
- Local set point Local set point specification
- Logic section logic circuit
- MCU clock MCU clock
- Microprocessor microprocessor
- Output control section output control
- Power supply power supply
- RAM section RAM memory
- Relay relay
- Relay driver Relay driver
- Signal conditioning Signal conditioning
- Time of day time base Time of day time base
- TOD clock Daytime clock
- Triac driver Triac driver
- Water level detectors ... water level detectors and temperature limit switches